Diacetylenes are compounds that can be represented by the formula R—C≡C—C≡C—R. The ability of diacetylenes to give rise to visibly coloured polydiacetylenes is known. Polydiacetylenes often exhibit polychromism, i.e. they can display more than one visibly distinct colour. Typically, when exposed to UV light, a diacetylene initially gives rise to a blue coloured polydiacetylene. Heating the blue polydiacetylene induces thermal perturbations into the polydiacetylene backbone that converts it into a red coloured form. Further heating of the red polydiacetylene will often produce a yellow polydiacetylene, but this species is usually transient and will revert to the red form upon cooling. Even though diacetylenes can be used in multi-colour imaging applications, they usually lack the ability to produce yellow and consequently orange and in particular green shades, and therefore true full-colour imaging is not possible.